Always create a fresh worktree (#3224)

* fix(server): always create requested worktrees

A slug is a preferred name, not workspace identity. Let the worktree creator suffix occupied paths and branches so duplicate and detached-slug requests still create fresh worktrees.

* fix(server): suffix occupied checkout branches

Fresh creation also applies when checkout targets are already in use. Create a suffixed branch from the requested branch instead of rejecting the request.

* test(server): align occupied branch coverage

* test(server): remove stale worktree reuse expectations

packages/server/src/utils/worktree.posix.test.ts

@@ -2,7 +2,6 @@
 /* eslint-disable max-nested-callbacks */
 import { describe, it, expect, beforeEach, afterEach } from "vitest";
 import {
-  BranchAlreadyCheckedOutError,
   createWorktree as createWorktreePrimitive,
   deriveWorktreeProjectHash,
   deletePaseoWorktree,
@@ -299,22 +298,17 @@ describe.skipIf(isPlatform("win32"))("worktree POSIX-only", () => {
       expect(currentBranch).toBe("release/1.1.15");
     });
 
-    it("throws a typed error when checking out a branch already checked out in the main repo", async () => {
-      let caughtError: unknown;
-      try {
-        await createLegacyWorktreeForTest({
-          cwd: repoDir,
-          worktreeSlug: "dev-worktree",
-          source: { kind: "checkout-branch", branchName: "main" },
-          runSetup: true,
-          paseoHome,
-        });
-      } catch (error) {
-        caughtError = error;
-      }
+    it("creates a suffixed branch when checking out a branch already checked out in the main repo", async () => {
+      const result = await createLegacyWorktreeForTest({
+        cwd: repoDir,
+        worktreeSlug: "dev-worktree",
+        source: { kind: "checkout-branch", branchName: "main" },
+        runSetup: true,
+        paseoHome,
+      });
 
-      expect(caughtError).toBeInstanceOf(BranchAlreadyCheckedOutError);
-      expect((caughtError as BranchAlreadyCheckedOutError).branchName).toBe("main");
+      expect(result.branchName).toBe("main-1");
+      expect(existsSync(result.worktreePath)).toBe(true);
     });
 
     it("fetches a GitHub PR branch, checks it out, writes metadata, and runs setup", async () => {

packages/server/src/utils/worktree.ts

@@ -207,13 +207,6 @@ export interface CreateWorktreeOptions {
   worktreesRoot?: string;
 }
 
-interface ResolveExistingWorktreeForSlugOptions {
-  slug: string;
-  repoRoot: string;
-  paseoHome?: string;
-  worktreesRoot?: string;
-}
-
 export class BranchAlreadyCheckedOutError extends Error {
   readonly branchName: string;
 
@@ -1063,38 +1056,6 @@ export async function listPaseoWorktrees({
     );
 }
 
-export async function resolveExistingWorktreeForSlug({
-  slug,
-  repoRoot,
-  paseoHome,
-  worktreesRoot,
-}: ResolveExistingWorktreeForSlugOptions): Promise<WorktreeConfig | null> {
-  const worktrees = await listPaseoWorktrees({
-    cwd: repoRoot,
-    paseoHome,
-    worktreesRoot,
-  });
-  const slugSuffix = `${sep}${slug}`;
-  const existingWorktree = worktrees.find((worktree) => worktree.path.endsWith(slugSuffix));
-  if (!existingWorktree) {
-    return null;
-  }
-
-  const { stdout } = await runGitCommand(["branch", "--show-current"], {
-    cwd: existingWorktree.path,
-    envOverlay: READ_ONLY_GIT_ENV,
-  });
-  const branchName = stdout.trim();
-  if (!branchName) {
-    throw new Error(`Unable to resolve branch for existing worktree: ${existingWorktree.path}`);
-  }
-
-  return {
-    branchName,
-    worktreePath: existingWorktree.path,
-  };
-}
-
 export interface DeletePaseoWorktreeOptions {
   cwd: string | null;
   worktreePath?: string;
@@ -1375,7 +1336,12 @@ async function resolveWorktreeSourcePlan({
         }
       }
       if (await isBranchCheckedOut(cwd, source.branchName)) {
-        throw new BranchAlreadyCheckedOutError(source.branchName);
+        const branchName = await resolveUniqueLocalBranchName(cwd, source.branchName);
+        return {
+          branchName,
+          metadataBaseRefName: source.branchName,
+          addArguments: ["-b", branchName, "--no-track", source.branchName],
+        };
       }
 
       return {